Training in zone 3: the staple diet for an endurance cyclist

What is ‘Zone 3’?

Zone_3_physiologyLike zone 2, zone 3 training will lead to enhanced endurance fitness. However, in contrast to zone 2, which could be viewed as ‘preparation to train’, zone 3 is more aggressive in nature, leading to far more striking physiological adaptation. Don’t be tempted to read that line and see it as a short cut to good endurance preparation though! You need the time in zone 2 to enable you to make the most of zone 3 work (we have a whole factsheet on the “1-2” approach of these zones, see ‘Pushing and pulling the lactate threshold’).

Zone 3 is the range of exercise intensity between your two ‘lactate thresholds’: the first being where lactic acid concentration in the blood starts to accumulate (left panel on the figure below); the second being where the body can no longer stabilise blood lactate (right panel on the figure below). Training in this region (65 to 80% VO2max) is therefore critical to helping the body deal with the metabolic consequences of lactic acid production. Our video on lactate threshold testing explains how we test for these key physiological landmarks.

Why would we use Zone 3 training?

We know the blood lactate response to exercise to explain an athlete’s ability to perform in endurance events. Once we have spent time ‘pushing up’ the lactate threshold from below, we can switch to ‘pulling it up’ by working in zone 3.  A good analogy for zone 3 is as a kind of ‘stepping stone’ taking you from pure base training to racing, hence why it will appear at that point in your periodised year (see below). There are two other instances where zone 3 training is useful to have in your armoury:

•    to develop fitness when you are short of time

•    to maintain endurance volume in the race season when training is dominated by shorter, more intense sessions.

Again, don’t think this means you can skip zone 2 work: too much zone 3 too soon is a shortcut to overtraining. Zone 3 is the double edged sword of the training intensities: a time efficient, high return zone; but too much can be a slippery slope. Optimizing just the right balance between the dose of training and the amount of recovery is essential.

What part of the periodised year would I train in Zone 3?

Zone 3 is best used in the transition from your base miles to your race season build (i.e. zone 4). There comes a time when the returns from continued Zone 2 emphasis diminish, so it makes sense to up the training intensity rather than the duration to increase overall load. Typically, the coach would i) integrate blocks of zone 3 work into longer zone 2 sessions and then, ii) build the overall time spent in zone 3 to a point where whole rides are completed at ‘tempo’. For most people beginning to race in April, February and March would be the time to consider this approach. At the 2010 PBscience Winter workshop, Dan talked through some of key considerations in planning your training in a presentation entitled Approaches to Periodisation.

What are the benefits training in Zone 3?

Since Zone 3 sits between the two important landmarks of the lactate profile, you would rightly assume that training in that region impacts on the body’s ability to retard lactic acid production, speed its removal, and importantly, to maintain a high rate of energy turnover necessitated when using the lactic acid energy system. Indeed, the biggest adaptations from training in this region are:

•    increased mitochondrial enzymes (these will help oxidise the lactate being produced)

•    increased muscle glycogen storage (as the body is using more carbohydrate during exercise at this intensity, the body prepares for that)

•    optimising the properties of the fast twitch muscle fibres (which are recruited more and more above LT) to make them more ‘oxidative’

•    producing a strong network of capillaries in the muscle (helping oxygen delivery to, but also removal of lactic acid from, the muscle)

What can we expect from Zone 3 training?

The athlete training in Zone 3 is likely to experience the following:

•    Requires relentless focus to maintain, easy to lose power if you “take your eye off the ball”

•    Breathing regular, unable to have a constant conversation

•    There is a sensation of leg effort now, with it often being a challenge to keep going to the end of the ride

•    Complete recovery normally within 24 hours if nutrition is prioritised during and post ride.

A special note on nutrition strategies for training in this zone

Since these sessions are above LT, and are therefore fuelled predominantly by carbohydrate, zone 3 eats body glycogen stores at a considerable rate – obviously, not to the same extent as zone 4 – but because duration of sessions is still reasonably high (reaching 2 to 3 hours by the end of a dedicated training mesocycle), daily calorie intake may need to be doubled (a 3 hour ride in zone 3 can require upwards of 2500kcal!)

A note on ‘Sweetspot’ training

Sweetspot” is an incredibly in vogue phrase within cycle training. It refers to a region at the very top end of zone 3. The underlying principle of sweet spot training is a balanced amount of intensity and volume that produces a maximal increase in an athlete’s second threshold: around 25 mile time trial pace, or the maximal intensity you could hold for an hour’s effort[1]. It is suggested that work in this range will build simultaneously your base as well as the power at second threshold... thus the nickname, “sweet spot”. This is shown in the graph (taken from Dr. Andy Coggan, Ph.D).


Typical sessions

Training using Zone 3 would typically evolve from repeated, short blocks within a zone 2 ride, to complete rides at this intensity (starting with 1.5 hours, reaching 3 hours in experienced riders). A particularly aggressive training block would be a 3 day block of 3 x 3 hours – not for the faint hearted!


Use of sweetspot training should follow previously explained training principles: it is not a replacement for endurance base, and should only be used having built up to it. This is why we include it here: it is the next step up in your training regimen:

  • Add it into your training having worked to build the hours in the lower / mid range of zone 3 first.
  • Build the time you spend in the sweet spot (moving from 10 minute blocks, to building to 4 x 20 within a ride for experienced riders with a good endurance ability).

[1] this function definition has lead to the term functional threshold power, or FTP.

Message to take home:

The fundamentals to effective Zone 3 training are: sound nutrition, mindful recovery, gradual progression and consistency of effort. It is incredibly potent if handled well. However, watch how you cope with the load, and pay particular caution to missed sessions – be patient, and focus on the rate of progression: DON’T leap back into the plan, but instead, take a step back and re-build.

<!--[if !vml]-->
  <!--[endif]--><!--[if !mso]-->

Typical sessions

Training using Zone 3 would typically evolve from repeated, short blocks within a zone 2 ride, to complete rides at this intensity (starting with 1.5 hours, reaching 3 hours in experienced riders). A particularly aggressive training block would be a 3 day block of 3 x 3 hours – not for the faint hearted!

<!--[if !mso]-->
<!--[endif]--><!--[if !mso & !vml]--> <!--[endif]--><!--[if !vml]-->